This invention relates to communication between control units.
In some cases, separate electronic control devices including microcomputers are connected via a common data link to provide communication therebetween. For example, in some modern automotive vehicles, separate microcomputer-based control devices such as an engine control unit, a transmission control unit, and a shock absorber control unit, are connected via a common data link to communicate with each other. In such an automotive communication system, sensors detecting control parameters are generally connected to nearest control units respectively. Control data signals derived through the sensors are transmitted between the control units via the common data link. In the case of communication of the token bus type, transmission rights (called "tokens") to send data signals are circulated through the control units in a predetermined sequence or pattern.